prefix-export-limit (Protocols IS-IS)
Syntax
prefix-export-limit number;
Hierarchy Level
[edit logical-systems logical-system-name protocols isis level level-number], [edit logical-systems logical-system-name routing-instances routing-instance-name protocols isis level level-number], [edit protocols isis level level-number], [edit routing-instances routing-instance-name protocols isis level level-number]
Description
Configure a limit to the number of prefixes exported into IS-IS.
By default, there is no limit to the number of prefixes that can be exported into
IS-IS. To configure a limit to the number of prefixes that can be exported into
IS-IS, include the prefix-export-limit statement. The
prefix-export-limit statement protects the rest of the network
from a malicious policy by applying a threshold filter for exported routes.
The number of prefixes depends on the size of your network. Good design advice is to set it to double the total number of IS-IS Level 1 and Level 2 routing devices in your network.
If the number of prefixes exported into IS-IS exceeds the configured limit, the
overload bit is set and the overload state is reached. When other routers detect
that this bit is set, they do not use this routing device for transit traffic, but
they do use it for packets destined to the overloaded routing device’s directly
connected networks and IP prefixes. The overload state can be cleared by using the
clear isis overload
command.
The
show isis overview
command displays the prefix export limit when it is configured.
You can prevent IS-IS from enterning the overload state even after the prefixes reach
the configured limit, by using the
no-overload-on-prefix-export-limit
command.
Options
number—Prefix limit.
Range: 0 through 4,294,967,295 (232 – 1)
Default: None
Required Privilege Level
routing—To view this statement in the configuration.
routing-control—To add this statement to the configuration.
Release Information
Statement introduced before Junos OS Release 7.4.